Quantum
by Vixen Argentum
Summary: 100 years ago, Kisuke made it through his trial unscathed and has remained captain of the 12th. The hogyoku did not work, many lives were lost, and to fill the vacancy of his lieutenant, he promoted Mayuri. Now, there are strange space time anomalies occurring in Soul Society. Due to another universe intersecting, two of the same, but now very different people meet one another.


**Full Summary**

One hundred years ago, Kisuke made it through his trial unscathed and has remained captain of the 12th. The hogyoku did not work, and many lives were lost, and to fill the vacancy of his lieutenant, he promoted Mayuri.

Now, there are strange space time anomalies occurring throughout Soul Society, with souls seemingly from other universes being swallowed up by some and deposited in others. While Mayuri researches this and shares his findings with Kisuke...they are interrupted by another breach and find a very unexpected person in Kisuke's bedroom. Someone who's convinced that it belongs to him instead.

For UraMayu Week 2019

**Author's Notes:**

Sooo I had this vague idea about a fic where a universe exists where Mayuri and Kisuke are together...and they find a universe where they are not and help them get together. Or maybe a universe where they were apart and then they witnessed how good it was and yeah...who knows it was all half baked.

But uh...I sat down to write it...and this is apparently what I wrote instead, and it keeps on building and having ideas interconnect. So yes. What I meant to be a one shot...is probably going to be much larger.

I hate to have so many WIPs right now, but considering that it's UraMayu week...I'm going to publish any idea that comes into my head. As now I'm done with school and can return to writing. Finally. Consider me back in business.

* * *

It has been one hundred years since Kisuke had been through the trial. He'd survived with his life and freedom intact, that's true, but it was _also_ true that nobody believed him about the conspiracy behind Aizen Sousuke. It was a very lucky constellation of events that he was witness to, and he's not fully sure just why things played out the way they did. The Central 46 has always operated in an opaque way, and some of their decisions he agrees with…and many others he does not. His hollowified comrades didn't make it, and the testimonies of everyone he'd been with agreed that he'd tried to save them, and thus anything forbidden was overlooked in a surprising leniency, and while the circumstances were regrettable, enough people had died, and too many leaders were lost, and the Kisuke was too valuable to let go. It was a strange turn of events, but for now he would take it.

Even so, he knows exactly why things have panned out the way they have. That must be Aizen's doing as well. He assumes that he's been overlooked, as the hougyoku still needs work. Or maybe it's a more simple answer—Aizen is a sadist. He doesn't trust Aizen's motivations for leaving him relatively spotless, but pinning blame in other places, all other people implicated, now dead. His position for this whole century has been a difficult one, sitting and seeing the captain of the 5th across from him at every meeting, knowing exactly what he's done, but also knowing that there is absolutely nothing that he can do about it. Likewise, those close to him have risen to positions too, and while Kisuke is brilliant, he can't force people to see truth. He doesn't choose captains after all. He knows there are secrets about the 3rd, the 5th and the 9th, and he's worked steadily to uncover them, but for now, he sees them every day, in a face off with his own personal vipers. It's hard to know who to trust, but at least he's not fully alone.

He'd lost his lieutenant that night. They'd just begun to forge a connection, and Hiyori's death was a devastating loss in a way he would have never predicted, both to himself, to the other lieutenants, and to many of his lower officers. Now there was no link back to the old 12th, and everything left was truly for his own molding. Though when it came time to fill the slot, he'd ascended someone else who was just as disagreeable as Hiyori in temperament, but at least they had an understanding.

He and Mayuri have run the 12th together now for over a century, a formidable, ability balanced Captain and Lieutenant pair. And after after a long time and a lot of work and many concessions, and for professional reasons very few people knew about it, but that once tense relationship had blossomed into even more. It isn't perfect. Nothing is. But there are few places that Kisuke can look for solace. And a brilliant mind is one of them.

xXx

Mayuri had been working on the soul volume restoration project for months. Oddly enough, it wasn't the usual culprits, and that frustrated him. Usually when these things happened, it was either quincies or an overload of hollow souls needed to be purified. But this was truly weird. Souls appeared in some places and disappeared in others. The pattern was seemingly random, but space time fabric appeared to be splitting and different universes were blending, exchanging things, and going back to normal but with completely different numbers of inhabitants. Thin fingers grasp a pen and scratch numbers and formulas down as he works to calculate things, but nothing he works out seems to be adding back up correctly. There's been another breach of this type—this is now apparently clear.

"You've been up all night," says Kisuke, behind him.

They are the only ones left in the laboratory. Everyone else has gone to sleep. He places one steady hand between Mayuri's shoulder blades. He feels him tense, and then relax. Touch isn't always easy for him, he knows, but so long as he waits, eventually he warms.

Gently he places a cup of steaming coffee beside him, and pushes it right in front. "I thought you might need this," he says. "I know you won't sleep if I tell you to, even if I tell you that I miss you."

Mayuri frowns. "That's exactly what won't get me into your bed," he says. "I'm busy, but I have at least found some new threads that I'm trying to follow."

Kisuke sits down beside him. He knows better than to push anything more, but Mayuri is right that this is a very vexing problem, and if they don't solve it, there may be repercussions that nobody had foreseen.

"Tell me," he says. "What have you learned?" Of all of Mayuri's features, piercing eyes, fragile build, laughing smile when he's found something that amuses him, his intelligence will be what he loves the best.

At the chance to share his knowledge, he can practically see Mayuri glow. Especially as this is a project that is his, and thus, he'll have information that Kisuke does not know.

"Well, you know how our world exchanges souls regularly between the Living World, Hueco Mundo, and Hell? This flow of souls is set up because the four worlds balance them out, with the Soul King directing flow in the middle. But there are an infinite number of parallel worlds, and instead of sitting on orthogonal planes to one another in a situation that balances them…these worlds exist overlapping with ours, and it seems that these soul hemorrhages and gains are between these universes and not the worlds we usually control the flow between."

Kisuke muses on the information. He'd known the basics of this for a long time, and it had fascinated him, especially with knowing how the soul king worked in directing the flow of souls. But his research into the parallel universes had never been a priority. In general interfering with them involved things that he knew were very illegal.

"That is an astute intuition," he says.

Mayuri sighs. "Remember the days when if there was an imbalance of souls, all we had to do was go out and kill a few thousand people?"

Mayuri reaches for the cup of coffee and sips it. He doesn't quite care for the taste, but he does desire the caffeine.

Kisuke laughs. "Now, now, Mayuri-san…if you start saying things like that, people might start to worry."

He knows that Mayuri means it though. And he does have a point. Crude as it is, that would be an easy fix. A secret sanctioned way to try out new weapons. A million other things that appear in the shady underbelly of the Gotei that he made peace with long ago. This problem is far more complex than that.

Mayuri continues.

"If I can't track which parallel universes have been opened and closed, I won't know if I'm accidentally destroying something needed in another world, and then with souls popping in and out of existence, surely the other versions of the Gotei in the other worlds are going to try and balance themselves and might accidentally destroy someone we need…" Golden eyes look off into the distance as he ponders his conundrums. He makes a sour face and lets his breath out in a hiss. "This is a mess."

He gets out a small electronic gadget, with a radar and buttons. "I've developed this sensor to detect openings into parallel universes rather than to orthogonal ones. But it seems that whenever there's a rift that opens one universe to another, the barrier between them is kind of like swiss cheese and where one opening exists several others are created, so it's difficult to tell where it's origin was. And of course, this makes the appearances and disappearances of souls more difficult to monitor or predict."

"Interesting." Kisuke picks up the sensor and views it. It's not picking up anything currently, but it has recorded activity, mostly in the evening, several nights in the past week.

There is an obvious question that Kisuke needs to ask.

"Since you've said that souls have been added as well as subtracted in these universes…then that must mean that you have encountered souls from another universe, is that right?"

Mayuri's eyes flash over him. "Yes…there have been odd instances in the Rukongai so far of duplicates of people showing up, but having no memory of things that are considered common events in our world, and instead claim that something else is true."

The ideas flicker in Kisuke's gaze. "Ah, so these universes are probabilistic. Universes where there was another chance of something happening, and thus, they have no knowledge of this one."

"Precisely," says Mayuri. "Something that can only be reached with a forbidden kido or a truly destructive universal force. So I think that if we—"

His words are cut short. The device on the table starts blinking and beeping. Mayuri's face lights up and he peers at the screen.

"It looks like we're in luck. The nearest tear is only a short distance from here, within the 12th's compound." He squints at the screen. "In…your bedroom, it looks like…of all things."

Kisuke grins. "Well, I though you said I wouldn't be getting you in there. I'm right again, you see."

Mayuri rolls his eyes. "You are immature and infuriating." But his expression softens. "Lets go."

The two of them shunpo towards the destination, almost in an adrenaline filled race. Another light shows up on the sensor in Mayuri's hand. "A soul has dropped in there! Quick! Hurry! Before the window closes and it possibly goes back in."

They've pushed themselves to the limit and are nearly panting as they get there. Kisuke throws open the door and Mayuri follows him through it, but then they're both halted in their tracks.

Right in the middle of the room is someone, who based on the facial features and costuming and stature, could only be Mayuri…but he wears the distinctive olive silk lined haori of a 12th division captain. He and Kisuke eye each other, and they're both stunned. Kisuke opens his mouth as if to speak, and then he sees this Mayuri's face twist into disappointment and disgust.

"What are you doing in my room?" he demands.

Kisuke is taken aback for a second, realizing possible implications of this man in this room wearing these clothes. But he quickly regains his composure and gives a friendly smile. "Well, actually, this is my room," he says.

"Impossible. You haven't been welcome here in—" Now it's this other Mayuri's turn to stop and stare.

Kisuke looks back at his Lieutenant who is now in a frozen staring contest with their new visitor. They have completely different adornments and clothing, but still, it's one mirror looking into another, and both are transfixed. Both are the butterfly and both are the pin. Expressions are both characteristically expressive and unreadable, a unique quirk of the man he's grown to care for.

"Oh." says the visitor. There's a long pause, but then he stands up straight and continues. "I've heard of things like this happening in theory, but never in my wildest dreams did I imagine that I'd find myself living in my _own personal hell_."

He sees the pride twist in his Lieutenant, a mix of anger and disbelief, and still wonder and curiosity and a billion emotions to process that he knows that no variation of Mayuri's mind will be able to process efficiently. With one hand he pulls back on Mayuri's shoulder, and Mayuri is still somewhat too shellshocked to react and merely lets his hand hang, but the gesture is not lost on the newcomer, who looks back at Kisuke now with a mixture of rage and confusion, and something that he can't quite name.

"Well now," says Kisuke. "Clearly we have a lot to talk about and do," he says. "My Lieutenant has been working on a project about some odd soul exchanges. Surely you understand that three minds to brainstorm would be better than two, yes?" He restores his cheerful demeanor. "Come with me, and we'll both sit down and tell you about it."

And with that, a very awkward ménage a trois makes their way down to the sitting room in the Captain's quarters.


End file.
